Jami` at-Tirmidhi 610
جامع الترمذي#610Da'ifAli bin Abi Talib (may Allah be pleased with him) narrated that :the Messenger of Allah said, about urine of a male child that suckles: "The urine of the boy is sprinkled, and the girl's urine is washed." Qatadah (one of the narrators) said: "This is so, as long as they do not eat, when they eat, then both of them are washed
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Zubair Ali ZaiDaif
In-book reference: 6:67